Abstract: A sternal retractor for use in internal mammary artery dissection comprises a rack bar having fixed and movable spreader arms, the blade-carrying parts of which are rotatable to, and lockable in, several discrete positions. The blades are carried by slides on the spreader arms, and are pivotable about two mutually perpendicular axes which are also perpendicular to the arms, but restrained against rotation about axes extending lengthwise of the arms. One of the slides disclosed is provided with an undercut slot to receive a post for mounting auxiliary retractors. This makes the retractor especially useful for various operation in addition to internal mammary artery dissection.